Refactor any to not use any const_casts

Consider this a followup to #115. There's no need to use const_cast,
since it's very easy to make it work in a const-correct manner.

Option to disable example building

c-code in manual upated

added locality-sensitive hashing to Matlab wrapper

Fix to memory errors signalled by valgrind in flann::any. 

Making a copy of the dataset in when building the index in the Matlab mex file to fix the issue of Matlab releasing the memory after index was built.

Python bindings: raise KeyError if you give a bad param name

Fixed link error on MinGW and MSYS

Include path fix

Put local include dir at the beginning of include path, so that system-wide installed flann headers don't get included.

Small documentation edits