Add installation instructions to sphinx docs
Don't include private members in sphinx docs
Correctly link par_loop to pyop2.op2.par_loop in sphinx docs
Make wrapper code a private variable
Miscellaneous documentation fixes
Merge branch 'doc-fixes'

* Add installation instructions to sphinx docs
* Don't include private members in sphinx docs
* Correctly link par_loop to pyop2.op2.par_loop in sphinx docs
* Make wrapper code a private variable
* Miscellaneous small documentation fixes