Fix templates files overwriting sample files

Caused by a templates defining a file, and then the
sample defining a filw with the same name. This CL
contains two fixes:

1) Rename the strings.xml file in the FragmentView template
which overwrites a sample's strings.xml.

2) Change the build.gradle so that the emitGradle task
fails when it hits this problem.

Change-Id: I7af2106385fd59f33b8cb82717fc485fda9acd34
2 files changed