cf logs add support for manifest files

[StephenDillon]

Please provide details on the following items. Failure to do so may result in deletion of your feature request.

What's the user value of this feature request?
A quick way to tail the logs without needing to add the app name, enabling faster development, more reliably picking up the name of the app you pushed with and easier scripting

Who is the functionality for?
Developer productivity

How often will this functionality be used by the user?
Daily

Who else is affected by the change?
Net addition

Is your feature request related to a problem? Please describe.
cf logs <APP_NAME> is a pain to script and a bit slow to type out.
It would be great if we could do cf push and have it take the default manifest as it does for cf push

Describe the solution you'd like
cf logs uses the same logic as cf push , checking for a default manifest.yml or -f to take a custom named manifest.yml file

Describe alternatives you've considered
I use the below bat script to quick build/deploy but it doesnt work if the dir name is different from manifest. It might be possible to improve and parse the manifest file to extract the push name but it would be great if it was supported with the same support cf push has.
`@echo on
CALL gradlew clean build -x test
for %%I in (.) do set CurrDirName=%%~nxI
echo %CurrDirName%

CALL cf push
CALL cf logs %CurrDirName%`

[cf-gitbot]

We have created an issue in Pivotal Tracker to manage this:

https://www.pivotaltracker.com/story/show/177010040

The labels on this github issue will be updated when the story is started.

[icyerasor]

I'm in favor of this.
Scripting becomes redundant if you have to provide the app name of the app you just pushed with push -p jarFile.jar -f manifest.yml getting the app-name out of the (possibly stage specific) manifest automatically.