add git specific files and submodules

Third party libraries extjs and mathjax are handle via git submodule.
Ignore the eclipse project file.

.gitignore

+.project

.gitmodules

+[submodule "static/plugin_extjs"]
+	path = static/plugin_extjs
+	url = https://github.com/probonogeek/extjs.git
+[submodule "static/plugin_mathjax"]
+	path = static/plugin_mathjax
+	url = https://github.com/mathjax/MathJax.git

plugin_extjs @ 6746dc89

+Subproject commit 6746dc89c47ed01b165cc1152533605f97eb8e8d

plugin_mathjax @ da8d4885

+Subproject commit da8d4885fb70c09624dfef641e0f326e9961bb24