Remove useless Assembler:: on constant lookups

Before I used the Assembler::<sub-module> shortcut to define my
sub-modules.  This removed Assembler from the module nesting for
constant lookup.  So I had to prefix all my constant lookups with
`Assembler::`.  Now I use the full module nesting in defining
sub-modules, so the Assembler module is included in the module nesting
for constant lookup.  So I removed the useless Assembler::