Import NonLockingScrollView from AOSP Email client.

As contained in current AOSP master:
https://android.googlesource.com/platform/packages/apps/Email/+/b3c37a31ccffe137cc9b1c1068bb99d3d00a2ee4
Switch to using NonLockingScrollView

This implements the AOSP Email solution for incorporating
a Webview inside a ScrollView, while still being able to
scroll diagonally.

This replaces the functionality of TitleBarWebView (which
is now removed).
Revert auto-scroll changes that are no longer needed.

Revert "Only Jelly Bean seems to have the auto-scroll issue"

This reverts commit a3802a7a8eece86f31070868f9ba7c9c7b23f92e.

Revert "Hack around WebView's initial auto-scrolling past the message header"

This reverts commit 8dcc769c50ab4cfb7c5b8f8f9b5bed3fd28801c2.

Conflicts:

	src/com/fsck/k9/view/MessageWebView.java
Import RigidWebView from AOSP Email client.

Also import prerequisite classes.

As contained in current master:
https://android.googlesource.com/platform/packages/apps/Email/+/b3c37a31ccffe137cc9b1c1068bb99d3d00a2ee4
Move AOSP files.

Patch RigidWebView for K9.
MessageWebView would need to extend RigidWebView.
NonLockingScrollview fixes.

Implement methods missing in API 7

Fix coordinate reference frame mismatch.  Touch events are
relative to the view display, whereas view children are relative
to the view.
Use non-deprecated constants
LinearLayout fill_parent

(Don't think it really matters.)
Fix missing 'download remainder' button.
Merge pull request #415 from zjw/non_locking_scroll_view_rebased

Kit Kat UI issue
Sadly, KitKat's file manager fails to recognize our mimetype and won't let users import settings
changelog for 4.701
Bumped manifest to 4.701
Updated Japanese translation of the changelog.
Fixed typo.
Upgrade Gradle build files
Add Gradle wrapper
Fix file selection for import

Using FLAG_ACTIVITY_NO_HISTORY will cause the file selection
to fail when KitKat's "Open from" activity opens a third-party activity.
With the new webview scrollview combo we've got loadinoverviewmode seems to behave better.