Build as a Shared Library

[SSoelvsten]

It is not possible to build Adiar as a shared library. Some user's would like to build Adiar once and then install it. This way, you do not need to include it as a submodule to each of your projects (and build it for each of them independently). Furthemore, allowing this would make Adiar usable in closed-source projects (by circumventing TPIE's LGPL v3).

Note:
This should then also be made to work with CMake's find_package.

Note:
People may depend on multiple versions of Adiar. Hence, one should install it with the version number suffixed. Look here for how to do so.

[SSoelvsten]

If the user at this point sets ADIAR_SHARED to ON then CMake will crash - there is no reason for it to cryptically fail and have tons of settings that are only related to building it as a shared library.