Enable Linux builds

[davemevans]

As it stands, it isn't possible to build this project on Linux for a number of reasons:

• There are a number of mixed casing issues in filenames and code which are obviously OK on Windows but not on Linux. Addressed by making filenames and references to them more consistent.
• libcurl was using a Windows-specific name which caused linking to fail due to the missing library. This is addressed by using find_package to locate the library which works cross-platform.

Further, the project would not build on CentOS 7 (and other distributions with compilers that do not run in C++11 mode by default)

• Compilation fails because older version of g++ do not run in C++11 mode by default, and the code uses a number of constructs requiring this. Fixed by conditionally setting a compiler option if using a GNU C++ compiler that supports the required flag. This isn't ideal but means no CMake upgrade is required and that Windows builds should not be affected.

Finally, removed the UTF BOM from the start of a couple of files.

Note that I haven't actually tested this build process on Windows, but I believe the changes should be transparent.

[RufaelDev]

Thanks, indeed i did not get to testing on Linux, thanks for the contribution