[s1920] Do not use GLOB in CMake for source file lists

From the CMake documentation of the FILE command:
"We do not recommend using GLOB to collect a list of source files from your
source tree. If no CMakeLists.txt file changes when a source is added or
removed then the generated build system cannot know when to ask CMake to
regenerate."

(based on commit [12390] - f123635)

Signed-off-by: DasBlub <DasBlub@gmail.com>
[s1921] Fix typo in AUTHORS file - thanks @AwkwardDev

* also remove "(no author)" and "@" from the authors list
* merge nicks "Tassadar" and "Tassader"

[ci skip]

(based on commit 285709a)

Signed-off-by: DasBlub <DasBlub@gmail.com>
[s1922] Remove the PREFIX parameter from the CMake files and use the standard CMAKE_INSTALL_PREFIX parameter instead

This also fixes the behaviour with relative paths, until now, it
calculated the absolute path from the location of the top level
CMakeLists.txt instead of your current directory where you called cmake.

You need to re-run CMake and define CMAKE_INSTALL_PREFIX and remove
PREFIX! You can do so by either removing all files in your build directory
and start from scratch or run 'cmake -DPREFIX= -DCMAKE_INSTALL_PREFIX=<install_path> <path_to_source>'.
A check has been added to the CMake file to make sure that PREFIX is no
longer used.

(based on commit [12391] - d489531)

Signed-off-by: DasBlub <DasBlub@gmail.com>
[s1923] Add copyright header and some comments to .travis.yml

[ci skip]

(based on commit [12392] - 2ca7224)

Signed-off-by: DasBlub <DasBlub@gmail.com>
[s1924] reduce clone time in Travis by only getting the latest commit and not the whole history (default for travis is 100)

(based on commit [12393] - de0dcf7)

Signed-off-by: DasBlub <DasBlub@gmail.com>