Fix 'query' to show the correct list of changes

In a multi-query invocation the list of changes was being garbled.
Add normalize_date routine to standardize date normalization
Make 'query' output the complete owner's name

Previously it was truncating the names to a fixed length. Text::Table
takes care of finding out the correct column size. If we don't have it
we calculate the it ourselves now.
Substitute 'foreach' by 'for' to make the code uniform
Remove undocumented misfeature
Fix 'reviewer'

The /changes/$id/reviewers REST endpoint returns an array-ref and not
a list.
Use Text::Table to format 'reviewer' output
Assume the dependency on Text::Table

By assuming the dependency I could get rid of some weak formatting
code and simplify the code.
Only grok GIT_DIR when needed

We only need it in install_commit_msg_hook, which is invoked by 'new'
and 'push'. This way we avoid a Git invokation in all other
subcommands.
Reformat 'version' output when Gerrit is pre-2.7
v0.013

  [Changes]
  - Require, instead of just recommend, Text::Table and better format
    the output of 'git gerrit reviewer'.

  - The reviewer's names are always printed in full now.

  - Reformat the output of 'git gerrit version' when Gerrit is version
    pre-2.7.

  [Fixes]
  - Fix 'git gerrit query' to show the correct list of changes in a
    multi-query invocation.

  - Fix 'git gerrit reviewer' which was aborting when it tried to
    print the reviewer list.

  - Always strip the trailing zeroes from dates in the output of
    'query' and 'show'.