Templating benchmark functions
Context::finish() finishes all queues
Improved formatting of profiler output
Updated benchmark example

* Benchmark both single and double precision
* Take command line options

close #52
Fixing benchmark.cpp for g++-4.6
Suppress "comment withing comment" warnings

OpenCL 1.2 headers contain a comment withing comment block which leads
to noisy compile warnings.
Show OpenCL version in devlist output
Fix clang compilation flags

-Wno-comment was only enabled when libcpp was used.
Scatter data interpolation with multilevel B-splines
Boost.Preprocessor path for unconforming compilers

This makes MBA compilable with gcc-4.6 (and hopefully MSVC)
Updated README
Update README.md
Added MBA benchmark
Made multiexpression generation contexts persistent

This allows to reuse temporary and tagged expressions for different
multiexpression components.
Moved common members to detail::expression_context
Symmetric names for detail::assign_expression's arguments
Set up playground for type deduction experiments

refs #53
Partially works for terminals, still need to deal with expressions.
Logical expressions are easy

refs #53
Added nary expressions

refs #53

Assume that type of the nary expression result is the common type (in
std::common_type sense) of all operands.
Moving deduce_value_type transform to vexcl/operations.hpp

refs #53

I am convinced at this point that expression type deduction with Proto
transform is possible, so I am moving the mechanics to operations.hpp
and creating test for the type deduction correctness.