warnings: avoid string + int and use stringstream instead

See merge request !51

Fix shadowing warnings

See merge request !54

XdmfGridTemplate: use boolean && rather than bitwise &

See merge request !53

The code was useless before since it declared a variable that
immediately left the scope.

These instances are best fixed by renaming or removing the (unused)
shadowing declaration.

Fix warnings

See merge request !52

Since it is inherited, the destructor needs to be virtual to release
memory properly.

XdmfGridController: add missing `return` statement

See merge request !50

replace atoi for seek because that can get overflow easily

See merge request !49

With this we at least get full unsigned int range and a warning
if we overflow.

Cmake cleanup

See merge request !39

Set them at the top-level instead.

These were all overwriting each other otherwise.

This should be controlled by the build system.

The logic does not work with imported targets and CMake prefers to link
with absolute paths anyways.

For building shared and static libraries, using two different build
trees is best rather than trying to hack up a single build to do
multiple things.

There's no reason to special case this version of MSVC.

Set it only at the top-level and remove checks for policies which are
set to `NEW` and guaranteed to be so by the minimum version.

Revert the noboost work as it doesn't compile with visstudio 2013

See merge request !48