UMF versioning is doubled (and not compatibile with semver.)

[lplewa]

Current State:

We are currently using two different versioning schemes in our project:

• Main Version: This version is hardcoded in the CMake project command.
• Git Version (called "source version"): This version, compliant with Semantic Versioning (SemVer), is generated separately based on git-describe.

Expected state:

We should have a single versioning scheme, based on Git version which is compliant with SemVer

ref: https://semver.org/

[lukaszstolarczuk]

When fixing this issue we should also take into considereration this issue: #466

[lukaszstolarczuk]

Proposed solution to this problem is in: #616

We set CMake version just to use it for SOVERSION and to generate CMake FindUMF.cmake/config file.
UMF_VERSION after the change will be aligned to semver and used solely in the project.