New preference allows user to chose when terminal to calculate screen size.

Update of terminal size in onSizeChaged() event works well when terminal is run in "window" mode.
In this mode calculation in onMeasure() based on "WindowVisibleDisplayFrame" and "GlobalVisibleRect" produces wrong results
(see #10).

So onSizeChaged() works well with most of soft-keyboards(IME method).
Problem is that in some cases onSizeChaged() is not called if orientation is "landscape".
It depend of Android version and IME method.

Remark: In "full-screen" mode is restored use onMeasure() but with more simple implementation.

Resolves issue #17.

Existing logic was more suitable for "block" selection.

Related to fdroid/rfp#924

Related to fdroid/rfp#924

Related to fdroid/rfp#924

Prevents reported crash perhaps due to closed in background session.

Also warn user on activity restart

Code refactored to new activity class RemoteActionActivity where "path collection" functionality is managed as well.

Ensure horizontal scroll to allow import of long line.
Also add small improvements to layout.

Modification avoids some uses of session container.
Ensure always initialized session container.
Also reformat code of terminal service class and make NOTIFICATION_CHANNEL_APPLICATION private.

remove border and power button, enlarge and center terminal screen, increase size of text and add shadow

Remark: unlike Android Studio command line builds are not affected!

Switch allows use of more recent versions of "Gradle" and "Android Gradle plugin" in Android Studio.
For instance in Android Studio 3.2.1 build fail with error:
(*) case gradle 4.10.2 and gradle plugin 3.3.+:
...
Unsupported method: NativeArtifact.getSourceFolders().
The version of Gradle you connect to does not support that method.
...

(*) case gradle 5.+:
...
Failed to notify build listener.
...

Please revert this patch if you would like to use version of Android Studio before 3.3+.

As result in populateViewFlipper() and populateWindowList() indentation is changed.
Also refactor initialization of first session so that application finish immediately on error.

Prepare "Term Here" functionality for more advanced action processing.

Based on Android Studio 3.2 rules.

This fixes issues with "Open New Window" action where is requested terminal to switch to last window.