Add Firefox support

The release.bash script has been updated, and now depends on a helper
script called generateManifest.bash. A "--browser" flag (shorthand "-b")
has been added to the script in order to specify the target browser.

Now the manifest.json file is saved as a template at
templates/manifest.gjson (gjson stands for Generic JSON), which includes
conditional clauses which indicate what parts of the manifest are
applicable to each browser.

generateManifest.bash generates the src/manifest.json file.

Change-Id: Ib051f3d893045c1377007b9b076ffa7a702d9648
diff --git a/generateManifest.bash b/generateManifest.bash
new file mode 100644
index 0000000..dd7df4e
--- /dev/null
+++ b/generateManifest.bash
@@ -0,0 +1,15 @@
+# Generates the manifest.json file according to the dependencies passed
+# via CLI arguments
+dependencies=( "$@" )
+rm -f src/manifest.json
+cp templates/manifest.gjson src/manifest.json
+for dep in "${dependencies[@]}"; do
+  perl -0777 -pi -e "s/^#if defined\($dep\)\n([^#]*)#endif\n/\$1/gms" src/manifest.json
+perl -0777 -pi -e "s/^#if defined\([^\n#]+\)\n[^#]*#endif\n//gms" src/manifest.json