Merge branch 'develop'

* develop: (434 commits)
  [version-bump]
  Replaced the usage of `get_plugins()` with `file_exists()` when checking if a plugin version exists as the former can throw a warning.
  [languages] [update]
  [css] [debug] [compile]
  [version-bump]
  [clone-resolution] [ms] Improved the logic that restores the current blog when handling clones and switching to a specific blog later on is needed.
  [clone-resolution] [ms] When handling clones and switching to a specific blog is needed, also restore the current blog later on.
  [fs-lock] [update] Moved the addition of the `'fs_'` prefix for the lock into the lock constructor.
  [clone-resolution] [ms] [admin-notice] [ajax] Minor optimization.
  [clone-resolution] [ms] [admin-notice] [ajax] Fixed the clone resolution notice's network-level AJAX handler.
  [clone-resolution] [lock] [fix] Require the lock class when testing lock acquiring when trying to resolve a subsite clone.
  [clone-resolution] [lock] Prefix the ID of the lock that is used by the clone resolution mechanism with our prefix that is defined in the config.
  [clone-resolution] [fix] Removed the setting of the identification timestamp from `_handle_clone_resolution()` as it's now set from the main `Freemius` class.
  [clone-resolution] [new] Added another 60-sec lock for the clone resolution logic attempting to resolve a clone when duplicating a subsite.
  [clone-resolution] [storage-refactor] [major] * Transitioned into a flat storage structure (vs. array with keys). * Added a function to handle storage data migration to the new flat structure. * Made sure we reload storage from DB when accessing request_handler_* options to avoid race condition. * Make sure we reload `clone_identification_timestamp` from the storage when accessing it through `get_clone_identification_timestamp()` (again, related to race condition). * Removed `temporarily_clear_notices()`, which wasn't in use.
  [code-indentation]
  [option-manager] [enrich] Introduced a `$flush` param for `has_option()` and `get_option()` to allow reloading the data from the storage within the methods.
  [clone-manager] Turned the lock into a local var.
  [clone-resolution] [automatic-resolution] Use the new `url` param instead of `search`, which is more accurate for the current use-case (we want to find exact homepage match).
  [clone-resolution] [automatic-resolution] [locking] [refactor] Created a standalone generic `FS_Lock` class as the base system for locking, reverted the changes to the `FS_User_Lock` + updated the implementation with the usage of the new `FS_Lock` (seems like inheritance wasn't possible since the constructor of the base-class is public and the user lock is a singleton). In addition, instead of just checking if the lock is obtained before trying the automatic resolution, use `try_lock()` for 60 sect to check if locked and obtain the lock if not.
  ...

# Conflicts:
#	languages/freemius-cs_CZ.mo
#	languages/freemius-cs_CZ.po
#	languages/freemius-da_DK.mo
#	languages/freemius-da_DK.po
#	languages/freemius-de_DE.mo
#	languages/freemius-de_DE.po
#	languages/freemius-en.mo
#	languages/freemius-en.po
#	languages/freemius-es_ES.mo
#	languages/freemius-es_ES.po
#	languages/freemius-fr_FR.mo
#	languages/freemius-fr_FR.po
#	languages/freemius-he_IL.mo
#	languages/freemius-he_IL.po
#	languages/freemius-hu_HU.mo
#	languages/freemius-hu_HU.po
#	languages/freemius-it_IT.mo
#	languages/freemius-it_IT.po
#	languages/freemius-ja.mo
#	languages/freemius-ja.po
#	languages/freemius-nl_NL.mo
#	languages/freemius-nl_NL.po
#	languages/freemius-ru_RU.mo
#	languages/freemius-ru_RU.po
#	languages/freemius-ta.mo
#	languages/freemius-ta.po
#	languages/freemius-zh_CN.mo
#	languages/freemius-zh_CN.po
#	languages/freemius.pot
#	start.php

.gitattributes

@@ -1,14 +1,14 @@
 # Items to ignore when downloading a zip
-.codeclimate.yml export-ignore
+*.yml export-ignore
 .git export-ignore
 .github export-ignore
 .gitattributes export-ignore
 .gitignore export-ignore
-.travis.yml export-ignore
 gulpfile.js export-ignore
-composer.json export-ignore
+*.json export-ignore
 /languages/*.po export-ignore
 /assets/scss/ export-ignore
+*.css.map export-ignore
 
 # Declare files that will always have CRLF line endings on checkout.
 #*.php text eol=crlf