[entropy.const] drop several etpConst constants, replace with more OO vars

etpConst['clientdbid'] is kept for backward compatibility, but will be removed soon
While etpConst['serverdbid'] and etpConst['clientserverrepoid'] are gone.
[entropy.spm] PortagePlugin: fix xblast CONTENTS mangling when splitdebug=disabled

This is the exception generated by reading CONTENTS expecting valid UTF-8 encoded
text (while it currently is raw_unicode_escape):

stacktrace: Traceback (most recent call last):
  File "/usr/bin/equo", line 15, in <module>
    main()
  File "/usr/lib/entropy/client/solo/main.py", line 333, in main
    exit_st = func(*func_args)
  File "/usr/lib/entropy/client/solo/commands/command.py", line 335, in _call_locked
    return func(client)
  File "/usr/lib/entropy/client/solo/commands/install.py", line 183, in _install
    relaxed, multifetch, packages)
  File "/usr/lib/entropy/client/solo/commands/install.py", line 609, in _install_action
    exit_st = pkg.run(xterm_header=xterm_header)
  File "/usr/lib/entropy/lib/entropy/client/interfaces/package.py", line 4266, in run
    rc = self._stepper(xterm_header)
  File "/usr/lib/entropy/lib/entropy/client/interfaces/package.py", line 4251, in _stepper
    rc = steps_data.get(step)()
  File "/usr/lib/entropy/lib/entropy/client/interfaces/package.py", line 4153, in do_install_spm
    self.pkgmeta['installed_package_id'])
  File "/usr/lib/entropy/lib/entropy/client/interfaces/package.py", line 2262, in _spm_install_package
    spm_uid = Spm.add_installed_package(self.pkgmeta)
  File "/usr/lib/entropy/lib/entropy/spm/plugins/interfaces/portage_plugin/__init__.py", line 3078, in add_installed_package
    splitdebug_dirs)
  File "/usr/lib/entropy/lib/entropy/spm/plugins/interfaces/portage_plugin/__init__.py", line 2859, in __splitdebug_update_contents_file
    line = cont_f.readline()
  File "/usr/lib64/python2.7/codecs.py", line 675, in readline
    return self.reader.readline(size)
  File "/usr/lib64/python2.7/codecs.py", line 530, in readline
    data = self.read(readsize, firstline=True)
  File "/usr/lib64/python2.7/codecs.py", line 477, in read
    newchars, decodedbytes = self.decode(data, self.errors)
UnicodeDecodeError: 'utf8' codec can't decode byte 0xee in position 30: invalid continuation byte
Release Entropy 176
Tagging Entropy version 176
Revert "[entropy.qa] test_missing_dependencies: only consider direct dependencies"

This reverts commit a0037bfe762f79eb764f00d57baf79cf338f4df9.
It turned out that only considering direct dependencies is a no-go.
Also see:
http://www.flameeyes.eu/autotools-mythbuster/pkgconfig/dependencies.html
Release Entropy 177
Tagging Entropy version 177
[entropy.qa] fix the usage of get_deep_dependency_list
Release Entropy 178
Tagging Entropy version 178