WIP: Update test organization

[LarsAsplund]

This is work towards a clearer organisations as discussed in #4. The following changes have been evaluated

1. Added a new level of directories under the standard version directory. So far a basic directory has been added with the intention to contain tests evaluating basic support of features.
2. The new levels are complied into their own libraries, for example vhdl_2008_basic. This means that tests can be filtered based on language version and level
3. Examples of improved reporting and use of attributes to reference the LRM have been added, for example

         if run("Test downsizing of hexadecimal literal") then
            -- vunit: .LRM-2008_15_8
            value := 6x"0f";
            check_equal(value, std_logic_vector'("001111"), result("for 6x""0f"""));
         elsif run("Test upsizing of hexadecimal literal") then
            -- vunit: .LRM-2008_15_8
            value := 6x"5";
            check_equal(value, std_logic_vector'("000100"), result("for 6x""4""")); -- Fake a bug

4. Location preprocessing has been added to trace errors to file/line and pass messages have been enable. See examples here and here

[eine]

ui.add_library("vhdl_2008").add_source_files(join(root, "vhdl_2008", "*.vhd"))
ui.add_library("vhdl_2008_basic").add_source_files(join(root, "vhdl_2008", "basic", "*.vhd"))
ui.add_library("vhdl_2019").add_source_files(join(root, "vhdl_2019", "*.vhd"))

[bpadalino]

This is a really old PR - does it still apply?

[Paebbels]

@LarsAsplund is this PR maybe replaced by your new PR #14?

[LarsAsplund]

Yes, I think it can be removed. I'm doing general updates right now and I'm cherry-picking parts from other PRs that are relevant. Once that is done I can close the old PRs. The initial updates will be done today.

[LarsAsplund]

Obsolete