Get rid of the maven stuff.

Since Android project is moving towards a gradle based build system and
the support for the maven plugins were dropped, no point in keeping
these around still.
Update gradle.properties .

- Update the property names in gradle.properties to avoid ambiguity.
- Add extra properties required for maven POM deployment using
  uploadArchives .
Use jcenter() repository for dependencies.

Since jcenter() is a superset of mavenCentral(), this should not have
any negative effect on the build.
Update android plugin names in apply .

Use the recommended gradle android plugin names for library and
application projects.
Move PagerSlidingTabStrip to org.tuxdude.pagerslidingtabstrip .

- Rename the package, and move the source to the correct location.
- Update all references to the classes .
Move sample to org.tuxdude.pagerslidingtabstrip.sample package.

Move the sources in the sample project to
org.tuxdude.pagerslidingtabstrip.sample package.
Use ':' prefixed project names in settings.gradle .
Use the custom java maven deployer gradle plugin.

- The plugin uses doclava to generate javadocs
- Maven deployment configuration along with signing is also now
  available.