Tidy up AndroidManifest.xml

Formatting only; no functional changes
Don't export CoreReceiver
Don't "export" BootReceiver's scheduleIntent action
Remove now unused AccessibleEmailContentActivity
Change/fix indentation of Gradle files
Remove option to select (legacy) APG as crypto provider
Remove legacy APG interface
Remove APG permission
Remove unused strings
Merge pull request #498 from k9mail/manifest_fixes

Manifest fixes
Revert "Implement SSL file-based session caching"

This reverts commit 43c38a047feedda4720af5bfbc188a33f8dfaced.
Change text in feature graphic
Update changelog for 5.100
Support reading signing config values from Gradle properties
Bump version to 5.100
Set minSdkVersion + targetSdkVersion via build.gradle

Without this building with Gradle adds a 'maxSdkVersion' attribute to the manifest. This seems to cause the targetSdkVersion value being ignored. And with a targetSdkVersion value lower than 16 the permissions READ_CONTACTS/WRITE_CONTACTS imply READ_CALL_LOG/WRITE_CALL_LOG. But we don't need/want those permissions.
Update changelog for 5.101
Bump version to 5.101
Get more dependencies from jCenter
Merge remote-tracking branch 'k9mail_pgp_mime/master'

Conflicts:
	src/com/fsck/k9/activity/AccessibleEmailContentActivity.java