UI can now save and load to server.

app.yaml
	-login is required for the skill tree page

data.py
	-GetSkillTreeHandler is now complete
	-SaveSkillTreeHandler added to allow saving of skill trees

datatypes.py
	-semester_index property added to AssignedModule, to mark its location within a semester

scripts/script.js
	-added a removeModules global object in skillTree. This will keep track of assignedModules loaded from the server that were removed by user interaction. addModuleToTree() and removeAssignedModule() have been edited to reflect this.
	-saveToServer() complete. It will upload a stripped version of skillTree.assignedModules and removeModules as stringified JSON data
	-loadFromServer now takes in the GUID of the skill tree, and POST requests the server for the associated tree
	-the initial module list request on page load now takes into account modules that have been loaded by loadFromServer() before, and avoids overwriting crucial data. May need concurrency testing.

skillTree.html
	-template updated with loadFromServer call in the body.