Modernize CMake configuration

Refactoring based on practices of the Modern CMake approach:

* Set project version based on `version.txt` spec.
* Build shared libraries by default.
* Build tools and `geos-config` script.
* Add make `check` target to run `ctest` (no dependencies).
* Move failing/overlarge tests into `failure` directory.
* Add target to deploy Config-module with installed targets:
  `GEOS::geos`, `GEOS::geos_c`.
* Add basic uninstall target
* Add basic client example configured with CMake to use GEOS targets.

.editorconfig

@@ -37,6 +37,8 @@ end_of_line = crlf
 [CMakeLists.txt]
 indent_style = space
 indent_size = 2
+trim_trailing_whitespace = true
+insert_final_newline = true
 
 # CMake modules
 [*.cmake]

.gitignore

@@ -1,4 +1,5 @@
 /*build*
+/*install*
 aclocal.m4
 Makefile.in
 Makefile