add segmented control layout

[dreacot]

This PR adds segmented control to the cryptomaterial package, i was working on this as part of #166, but due to some changes to that PR and the fact that several other layouts would be needing it, i decided to add it as a standalone implementation.

This PR does not include the dragging animation which some segmented controls have, if it is desired it can be added at a later time. but for the sake of avoiding unnecessary delays, i have intentionally left it out

[Sirmorrison]

Do we really need a segmented control widget? we currently have a widget similar to this that is used on the send page.
cryptomaterial.SwitchButtonText.

[dreacot]

They are both different control layouts, what you are referring to is a button. The segmented control is used several places in the app, seems reasonable to make it a widget

[itswisdomagain]

Looks okay, but could be improved maybe?

[crux25]

Except for what has been pointed out by other reviewers, the PR LGTM.

[Sirmorrison]

This and we are good to go.

[Sirmorrison]

Since we are now using this, we will need to depreciate the switch text widget. So I recommend using this widget on the send page so we can test the implementation so far.

[dreacot]

This PR adds segmented control to the cryptomaterial package, i was working on this as part of #166, but due to some changes to that PR and the fact that several other layouts would be needing it, i decided to add it as a standalone implementation.

based on my original comment, i brought the segmented control widget out of my previous PR to make it non blocking. so trying to use it on another page takes us back the original problem

Since we are now using this, we will need to depreciate the switch text widget. So I recommend using this widget on the send page so we can test the implementation so far.

correct, the text widget would be deprecated, but not as part of this PR. the work on the send page can be done in another PR