4.7.0 Selectively run test subsets

This release adds the functionality for selective test execution as described in the new
test-suite usage information that prints after executing fpm test -- --help

Usage: fpm test -- [--help] | [--contains <substring>]
    
where square brackets ([]) denote optional arguments, a pipe (|) separates alternative arguments,
angular brackets (<>) denote a user-provided value, and passing a substring limits execution to
the tests with test subjects or test descriptions containing the user-specified substring.

For example, executing fpm test -- --contains string_t runs only those tests with the substring string_t in the test subject text and or the test description text.

See test/main.f90 and test/bin_test.f90 for examples of how to use the new test_description_t derived type and type-bound procedures to provide a similar help/subsetting capability to software packages that use the Sourcery library.

What's Changed

• Run tests selectively by @rouson in #76

Full Changelog: 4.6.1...4.7.0