Delegated in all ctors without time to those with time as parameter.

Using the new "util::getTime()" function all classes with 2 ctors, one with time and without time as parameter, that are otherwise similar, the timeless ctors now delegate to the ctors with time parameter.
Added some notes to "ReferenceList" class.
Fixed SimpleTag::createRepresentation to not allow Indexed LinkType

Closes issue #163
Merge pull request #165 from balint42/delegate_ctors

Delegated in all ctors without time to those with time as parameter.
Merge pull request #166 from balint42/fix_simpletag_linktype

Fixed SimpleTag::createRepresentation to not allow Indexed LinkType
Merge pull request #168 from jgrewe/units

unit scale estimation works correctly now
Tiny coding style fix: replace '){' with ') {'.
Merge pull request #167 from balint42/fix_codestyle

Tiny coding style fix: replace '){' with ') {'
add install target in CMakeLists, works for linux
changed naming in CMakeLists from pandora to nix
Merge pull request #170 from jgrewe/make_install

Defined Make install target in CMakeLists, changed naming to 'nix'

Nice!
DataArray::hasData() is now declared const (see issue #173)
Merge pull request #178 from jgrewe/const_has_data

DataArray::hasData() is now declared const (see issue #173)

LGTM
Value: call default constructor in copy constructor

This will properly construct the value object before we call
assign_variant_form(), which in turn will call set<T>() which will
call maybe_deallocte_string() and therefore access the dtype
member variable. The latter therefore has to be properly
initialised.
Merge pull request #182 from gicmo/ValueCopyCtor

Value: call default constructor in copy constructor
Value: Initialise uncertainty (double) to 0.0

This fixes the valgrind warning in TestDataSet::testValueIO:
"Syscall param write(buf) points to uninitialised byte(s)"
See issue #180
[test] Change tests of optional<T> to use operator bool()

This is part one of the fix for the build on osx, issue #181.
ImplContainer: Add operator!=(bool b)

We already had operator==(bool b). This is part two of the fix for
the build on osx, issue #181.
Merge pull request #184 from gicmo/osxBuild

Fix build on OSX. Closes issue #181
Merge pull request #183 from gicmo/ValueDoubleInit

Value: Initialise uncertainty (double) to 0.0
DataSet::Value: specialise the bool case to use 8bit size bitfield

For this we specialise FileValue<bool> to use an "unsigned char"
as the boolean storage (instead of bool directly) and then translate
this to (via NATIVE_B8) to STD_B8LE hdf5 types.
This should close issue #185