eigen: Use Eigen instead of Boost::uBLAS.
cmake: automagically downloading Eigen

and some tweaks and cleanup to 3rdparty CMake file
cmake: first search for system-wide Eigen3

only in case none found download sources
Merge pull request #6 from torbjoernk/feature/eigen-w-cmake

made CMake look for Eigen3
Merge branch 'pr/82/head' into development

* pr/82/head:
  cmake: first search for system-wide Eigen3
  cmake: automagically downloading Eigen
  eigen: Use Eigen instead of Boost::uBLAS.

Signed-off-by: Torbjörn Klatt <t.klatt@fz-juelich.de>
cmake: fix detection of system wide Eigen3 installations
Merge pull request #83 from torbjoernk/feature/fix-eigen3-detection

cmake: fix detection of system wide Eigen3 installations
polish up release notes
Merge branch 'release/v0.2.0' into development

* release/v0.2.0:
  polish up release notes
  examples: scalar: a few little cleanups
  removed const keywords in scalar_sweeper; they should be there, no idea why it worked even with them
  more documentation for scalar example; added mathjax directives at multiple points
  improved docu for scalar example; added ** at several points
  extended documentation for scalar example
  docu: extending/fixing/cleaning docu for upcoming release
  some enhancements of the coverage generation script
  fix for aggegrated coverage results
  cmake and tests: enable and provide test coverage analysis
  cmake: add option for GCC profiling
  sweeper: incorporate @memmett's remarks
  exceptions must be thrown to be effective
  some code formatting tweaks
  docu: some docu on IMEXSweeper::predict
  encap: some templatization tweaks