Implement float_precision parameter (Closes #31)

Added the ability to specify the amount of decimal digits (precision)
to be used when writing out (file or stream) a configuration.
Includes C & C++ versions.

As per zhaopingsun's suggestion

Merge fix for issue #41 from random85 ; Documentation and fixes by me

We look for the setting using its path and extract the setting name from the
path to get its index in parent for removal.

This adds "Removing a setting with its path" feature.
This changes the specification, the documentation has to be updated.

The test doesn't behave as documented. The wrong element is removed.

Octal ints

Add @include_dir directive: debian-style ("conf.d") config processing

Apply stylistic fixes, following Mark's advice: homogeneous style
with the rest of the code

 - Misc documentation fixes

 - Document the include_dir directive
 - Robustness: filter out non-files (where scandir supports it)
 - Add myself to the credits

  Quite some refactoring of the includefile stack and filename processing logic

  Adds some extra fields to scan_context, but does not change the API
  "symbols" file should hide all functions called scanctx_* anyway

Also, add x64 solution platform and DebugStatic/ReleaseStatic solution &
project configurations, generating static libraries.
Reset output and intermediate directories and filenames to VS defaults.
Adjust preprocessor definitions (LIBCONFIG_STATIC / LIBCONFIG_EXPORTS,
_USRDLL) for the static configurations.

Re-generate scanner.[ch], add aux-build/test-driver, and update documentation.

Re-generate scanner.[ch], add aux-build/test-driver, and update documentation.

A value is recognized as CONFIG_TYPE_INT if it's only numbers, and
CONFIG_TYPE_INT64 if it's numbers followed by L or LL. However from a
user point of view adding L or LL is confusing. Instead, if the
integer is too big to fit in an int, return a CONFIG_TYPE_INT64. This
also avoid silent truncation.

Add the existing tests and the examples. The testsuite is then run with
"make check".

Do not display compilation command lines, unless make is called with
V=1.

(which were infinitely recursive).