CamelIMAPXListResponse: Fix a documentation typo.
CamelIMAPXStoreNamespace: Rename 'path' member to 'prefix'.

Just so I can grok this stuff easier.  The 'path' member stored the
namespace prefix, minus any trailing mailbox separator character from
the NAMESPACE response (which btw is wrong; can't assume a namespace
prefix always has a trailing separator character.  e.g. a '~' prefix
for the "other users" namespace).
Remove unused camel_imapx_store_summary_namespace_new().
CamelIMAPXNamespaceList: Remove 'full_name' member.

The 'full_name' member is always identical to 'prefix', so not needed.
CamelIMAPXStoreSummary: Remove 'capabilities' member.

Was this intended for caching server capabilities locally?  WTF.
Thankfully we weren't actually using it for anything.
CamelIMAPXStoreInfo: Rename 'full_name' member to 'mailbox'.

I find the 'full_name' versus 'path' terminology to be very confusing.
Replace 'full_name' with 'mailbox' to match IMAP RFC terminology.
Rename CamelIMAPXStoreSummary API: 'full' to 'mailbox'.

The namespace code becomes a little clearer with these renames.

Renamed functions:

  - camel_imapx_store_summary_namespace_find_path
  + camel_imapx_store_summary_namespace_find_by_path

  - camel_imapx_store_summary_namespace_find_full
  + camel_imapx_store_summary_namespace_find_by_mailbox

  - camel_imapx_store_summary_full_to_path
  + camel_imapx_store_summary_mailbox_to_path

  - camel_imapx_store_summary_path_to_full
  + camel_imapx_store_summary_path_to_mailbox

  - camel_imapx_store_summary_full_name
  + camel_imapx_store_summary_mailbox

  - camel_imapx_store_summary_add_from_full
  + camel_imapx_store_summary_add_from_mailbox

  - camel_imapx_store_summary_full_from_path
  + camel_imapx_store_summary_mailbox_from_path