Composer over .gitmodules, basic installation script etc

This has been sitting in my repo for a while now so I thought I'd better put in a pull request before other people tackle the same issues.

**Changes:**
* moved to Composer to install Twig and Symfony packages.
* a basic installation script has been added (it's an aid to installation rather than a complete solution)
* some language issues were fixed that prevented functioning.
* added a pagination macro (uses Bootstrap style pagination)
* enabled use of smCore within a subdirectory (e.g. http://example.com/path/to/smcore)
* others as well, have a look at the commits for any further examples.

Some of my commits aren't well titled (the "hmm..." commit comes to mind) but they're usually only poor when the commit doesn't seem to change anything. I'm sorry that everything is in one big lump of changes - I don't know how I'd go about splitting the various changes apart.