[Conan] Migrated to more flexible conanfile.py.

- Required lib version can be in a range
- conan build ../path/to/source builds with conan specified compiler

conanfile.py

+from conans import ConanFile, CMake
+
+class OpenGeoSysConan(ConanFile):
+    settings = "os", "compiler", "build_type", "arch"
+
+    requires = \
+        "Boost/[>=1.56.0]@lasote/stable", \
+        "Shapelib/1.3.0@bilke/stable", \
+        "VTK/[>=6.3]@bilke/stable", \
+        "Eigen3/3.2.8@bilke/stable", \
+        "libgeotiff/1.4.1@bilke/stable"
+
+    generators = "cmake"
+
+    default_options = \
+        "Boost:shared=False", \
+        "Boost:header_only=True"
+
+    def build(self):
+        cmake = CMake(self.settings)
+        self.run('cmake "%s" %s' % (self.conanfile_directory, cmake.command_line))
+        self.run('cmake --build . %s' % cmake.build_config)

conanfile.txt

-[requires]
-Boost/1.60.0@lasote/stable
-Shapelib/1.3.0@bilke/stable
-VTK/7.0.0@bilke/stable
-Eigen3/3.2.8@bilke/stable
-libgeotiff/1.4.1@bilke/stable
-
-[generators]
-cmake
-
-[options]
-Boost:shared=False
-Boost:header_only=True