ImplContainer::getEntities use size_t instead of int for 'nT'

This fixes a warning on windows.
Merge pull request #120 from gicmo/win_fixes

ImplContainer::getEntities use size_t instead of int for 'nT'

LGTM
[test] Block::dataArrays() check filter (Type- and NameFilter)
Merge pull request #121 from gicmo/block_DA_filter_test

Add a test for Block::dataArrays() to check if the filter (Type- and NameFilter) work

LGTM :+1:
[win] Ignore warning C4251 for now (but see issue #124)
[win] Export all base classes of dll-interface classes (C4275)

This fixes instances of compiler warning C4275
Closes issue #78
DataSet::guessChunking: explicitly cast to double for csize

Fixes a compiler warning on windows about possible loss of data.
Merge pull request #125 from gicmo/win32_fixes

[win] Fix more warnings on windows
Use std::make_shared<> to create shared pointer

Using std::make_shared<>[1] will safe one allocation compared
to std::shared_ptr<T> tmp(new T(...)).

[1] http://en.cppreference.com/w/cpp/memory/shared_ptr/make_shared
Implemented use of "boost::optional" for some of the instances where "boost::none_t" was already being used:
mapping, unit, repository.
Not implemented for many yet to clarify cases: "dataType", "labels", "extents", "units", "values", "link", "extent", "metadata".
Merge pull request #128 from balint42/optional_branch

Implemented use of "boost::optional" for some more cases

Part of issue #86
Merge pull request #127 from gicmo/make_shared

Use std::make_shared<> to create shared pointer
ImplContainer behaves like bool and like boost::optional

It compares to boost::none and has isNone() method now.
[test] Complete tests for DataArray

This is part of issue #25
DimensionHDF5: Fix broken switch (missing break)
[test] DataArray: Enhance Dimension tests
Just some whitespace fixes. No logic change.
Merge pull request #129 from gicmo/balint_new

ImplContainer optional semantics and DataArray tests
(merge & rebase by @gicmo)
ImplContainer: Add backend() method for backend access

With backend the pointer managed by the shared_ptr<T> is
meant. The validity of the shared_ptr is checked before it is
returned and an exception is thrown if the pointer was found to be
invalid.

Part of fixing issue #76
Exception.hpp: Add missing sstream include