Add command and menu item to specify packages

This is less than perfect, because it lets some junk through, but it's
better than nothing.
Merge pull request #147 from david-christiansen/idris-set-idris-packages

Add command and menu item to specify packages
Clear the compiler notes when beginning load

The buffer is no longer killed on lack of contents in order to make it
easier to keep window layouts intact. It happens at the beginning of
loading to make slow typechecking less painful.

Fixes #123.
Merge pull request #148 from david-christiansen/issue/123

Clear the compiler notes when beginning load
Make module names in ipkg files clickable
Merge pull request #150 from david-christiansen/clickable-ipkg

Make module names in ipkg files clickable
Make C-c C-s deal with multi-line type declarations

Now there's some heuristics to find the right place to put the added
clause in the case of definitions like

    plusComm : (n, m : Nat) ->
               n + m = m + n

Instead of just putting the clause on the next line, like:

    plusComm : (n, m : Nat) ->
    plusComm n m = ?plusComm_rhs
               n + m = m + n

it finds a line that is indented the same or less than the original, producing:

    plusComm : (n, m : Nat) ->
               n + m = m + n
    plusComm n m = ?plusComm_rhs
Merge pull request #151 from david-christiansen/better-c-c-c-s

Make C-c C-s deal with multi-line type declarations
Allow filling paragraphs in LIDR files
Merge pull request #152 from david-christiansen/better-c-c-c-s

Allow filling paragraphs in LIDR files
Add clickability to Makefile and sourcedir

Also, be more robust at detecting modules
Add clickability to module imports in same package
Readme update for clickability
Add note on compatibility
Merge pull request #153 from david-christiansen/better-c-c-c-s

Clickable modules in source buffers, plus clickable Makefiles and sourcedirs in .ipkg
Allow setting the depth of proof search

This is done with a numeric prefix argument to C-c C-a.
Merge pull request #154 from david-christiansen/proof-search-depth

Allow setting the depth of proof search
Better message when deleting IBC
Allow partial loading of buffers
Describe region loading in README