Static definition of CSRs by default

This pull-request makes several changes to the structure of the User Manual:

1. Auto-generated tables of the CSR definitions are no longer prodcued by default. Instead, a set of static CSR definitions are now used to generate the html by default. (Auto-generation is still supported in the Makefiles.)
2. The access-type table in each CSR sub-section is deleted and a single instance of the table is now found in the Memory Map chapter.
3. All CSR sub-sections are moved into a csr-docs directory and appear in the same level of the Chapter hierarchy.
4. Minor cosmetic changes.

These changes were made to make updating the User Manual easier. None of the technical context has been changed.

Signed-off-by: Mike Thompson mike@openhwgroup.org