[confluence] change buttons to edit controls (see #4613)
[cleanup] drop unused code blocks in contextmenu from ancient skins.

Skins for 14.X should use a single background image (id 999) with border.
and must have a grouplist with id 996 for the context menu.
[cosmetic] change name of define to better reflect what it's for (old python guilib stuff)
[guilib] remove backward compatibility of converting edit controls to buttons.

For v14 ensure the following controls are edit controls:

SmartPlaylistEditor.xml:
 id 12, name of smart playlist

SmartPlaylistRule.xml:
 id 17, value of rule

DialogMediaSource.xml:
 id 12, name of media source

DialogNetworkSetup.xml:
 id 11, server address
 id 13, port
 id 14, username
 id 15, password
 id 16, remote path
[addons] adds GetDependencyVersion() to CAddon - used in place of GetXbmcApiVersionDependency
[guilib] adds APIVersion() to CSkin to determine which API version the skin wants.
[guilib] drop the separate default for the aspect ratio inside containers. It previously defaulted to keep unless the image was constant (not infoimage) where it defaulted to stretch. It now defaults to stretch like all images.
[guilib] remove inconsistent positioning of labels inside containers. <left> now mean left
[guilib] bump xbmc skin version to 5.1.0, still bw compat to 5.0.0
[cosmetic] drop unused function
[cosmetic] drop function definitions that no longer exist
[Confluence] bump version
[Confluence] label alignment fixes
[Confluence] image aspect fixes
Merge pull request #4613 from jmarshallnz/gui_drop_backcompat

[guilib] Drop back compatibility code and inconsistencies
Merge pull request #4627 from BigNoid/edit_buttons

[confluence] change buttons to edit controls (see #4613)
Merge pull request #4772 from ronie/confluence-4613

[Confluence] adjustments needed by PR4613
More efficient infobool expression evaluator

Expession infobools are evaluated at runtime from one or more single infobools
and a combination of boolean NOT, AND and OR operators. Previously, parsing
produced a vector of operands (leaf nodes) and operators in postfix
(reverse-Polish) form, and evaluated all leaf nodes every time the expression
was evaluated. But this ignores the fact that in many cases, once one operand
of an AND or OR operation has been evaluated, there is no need to evaluate the
other operand because its value can have no effect on the ultimate result. It
is also worth noting that AND and OR operations are associative, meaning they
can be rearranged at runtime to better suit the selected skin.

This patch rewrites the expression parsing and evaluation code. Now the
internal repreentation is in the form of a tree where leaf nodes represent a
single infobool, and branch nodes represent either an AND or an OR operation
on two or more child nodes.

Expressions are rewritten at parse time into a form which favours the
formation of groups of associative nodes. These groups are then reordered at
evaluation time such that nodes whose value renders the evaluation of the
remainder of the group unnecessary tend to be evaluated first (these are
true nodes for OR subexpressions, or false nodes for AND subexpressions).
The end effect is to minimise the number of leaf nodes that need to be
evaluated in order to determine the value of the expression. The runtime
adaptability has the advantage of not being customised for any particular skin.

The modifications to the expression at parse time fall into two groups:
1) Moving logical NOTs so that they are only applied to leaf nodes.
   For example, rewriting ![A+B]|C as !A|!B|C allows reordering such that
   any of the three leaves can be evaluated first.
2) Combining adjacent AND or OR operations such that each path from the root
   to a leaf encounters a strictly alternating pattern of AND and OR
   operations. So [A|B]|[C|D+[[E|F]|G] becomes A|B|C|[D+[E|F|G]].

I measured the effect while the Videos window of the default skin was open
(but idle) on a Raspberry Pi, and this reduced the CPU usage by 2.8% from
41.9% to 39.1%:

          Before          After
          Mean   StdDev   Mean   StdDev  Confidence  Change
IdleCPU%  41.9   0.5      39.1   0.9     100.0%      +7.0%
Where an infobool expression failed to parse, evaluate the infobool as false. Previously, this would result in a segfault due to the dereferencing of an uninitialised pointer to the head of the expression tree.
Add caching of infolabels

The functions CGUIInfoLabel::GetLabel and CGUIInfoLabel::GetItemLabel take
a number of strings returned from CGUIInfoManager::GetImage or
CGUIInfoManager::GetLabel, and combine them with various constant strings
which were determined during CGUIInfoLabel::Parse.

Rather than perform all the string operations on every call, this patch
changes to use a two-pass process: first it queries all the GetImage/GetLabel
strings, and then only if at least one of them has changed does it bother
rebuilding the resultant string - otherwise it re-uses the copy built on a
preceding call.

CGUIInfoLabel::GetLabel/GetItemLabel are also changed to return string
references, rather than forcing an additional string copy.

I have measured the effect while the Videos window of the default skin was
open (but idle) on a Raspberry Pi, and this reduced the CPU usage by 0.8%
from 36.2% to 35.4%:

          Before          After
          Mean   StdDev   Mean   StdDev  Confidence  Change
IdleCPU%  36.2   0.5      35.4   0.5     99.9%       +2.2%