Refactored MavenCentral interface

Renamed the MavenCentral interface to DependencyResolver (which is a more
accurate description of its purpose) and renamed its implementing classes to
MavenResolver and CachedMavenResolver.
Added ability to run Robolectric tests offline

Set the following system properties to activate the behavior:
  robolectric.offline=true
  robolectric.dependency.dir=<path>

Runtime dependencies will be retrieved from the specified path
instead of being downloaded from Maven.
Further renaming for consistency
Removed RobolectricTestRunner from DependencyResolver methods

Moved the configureMaven() method from RobolectricTestRunner to
MavenDependencyResolver, since it is only applicable there. This
means that DependencyResolver methods no longer require an
instance of RobolectricTestRunner.

THIS IS AN API-BREAKING CHANGE.

Instead of sub-classing RobolectricTestRunner to provide custom
Maven configuration, it is now necessary to subclass
MavenDependencyResolver.
Throw an exception when creating bitmaps with invalid dimensions.

Closes #1197.
Implement ShadowView.getOnCreateContextMenuListener.

Fixes #1194. Closes #1195.
Merge pull request #1189 from awrichar/offline

Added ability to run Robolectric tests offline.
Adding support to partial matching in ShadowIntentFilter.

This patch also fixed the issue with broadcast intents being
delivered solely based on the receiver action. This patch
also filters based on the data type as per spec.

Closes #1162.
Implement ShadowPopupWindow.showAtLocation.

Closes #1200.
Added new Config value for libraries

This config value specifies the paths to required Android
Library projects (relative to the project base dir). When
present, it supercedes the libraries from project.properties.

Also added a few constants in AndroidManifest.java to replace
hard-coded strings.
Basic activity-alias support.

Closes #1209.
Check for negative/zero input in createBitmap()

Adds a check for negative or zero values for Width/Height in
ShadowBitmap.createBitmap(int width, int height, Bitmap.Config config)
implementation. Raises IllegalArgumentException if params are negative
or zero. Follows implementation in android.graphics.bitmap.
Merge pull request #1216 from Graya3000/master

Check for negative/zero input in createBitmap()
Preserve stack map frames.
Merge pull request #1217 from cushon/master

Preserve stack map frames.
Compile with JDK 7 (default) and 8.
Merge pull request #1218 from robolectric/jw/jdk8

Compile with JDK 7 (default) and 8.
ResName constructor should trim() the attribute value passed in.

Badly formatted XML such as

      <item name="subtitleTextStyle">@style/TextAppearance.AppCompat.Widget.ActionMode.Subtitle
        </item>

Note the wrapped text content causes the actual string passed in to be followed with a CR and whitespace.

Real android handles this formatting fine, so should Robolectric
Implement TestHttpResponse.getContentEncoding.

Closes #1219.
Adding method to FragmentTestUtil to start a visible fragment with a
custom activity class and container view ID.

Closes #1206.