Bugfix: taxon names in the gene-tree displays

The taxon names are found directly on the species-tree nodes.
They can be overriden by the "ensembl alias name" taxon tag.
Get the display species-sets from ncbi_taxa_name

The list of species sets is now stored in the ncbi_taxa_node table.
Only the set of low-coverage species has to be fetched in a different
way.
Simplify the "genetree_display" logic

The "genetree_display" key is there by construction of the hash.
There is no need of checking it.
attrib_type codes have changed, updated to match data in 75
added readthrough counts
The method can be found from the mlss_id
Do not group "minor" slices into "Others"
New methods / documents to automatically display stats about gene-trees
Code to draw a tree

The drawing is made inside of a HTML table. Each branch / node is
assigned to a cell of the grid. The code assumes that several images are
available under the same URL (ct_hor.png, etc)
The gene-tree statstics are split in several pages
New columns in the table for wga stats

The columns show the raw values of number of base-pairs in the
alignment. There is a colour code to highlight low values of the
coverage. Strangely, sorting doesn't work
Replace the url action 'Summary' by 'Explore' for Variation and Structural Variation
Various bug fixes and features for genomic alignments including a table of overlapping alignments and alternating shades for blocks.

Bio/EnsEMBL/GlyphSet.pm => Removed scaling constraint from draw_cigar_feature method.
Bio/EnsEMBL/GlyphSet/_alignment_multiple.pm => Added alternating shades to GenomicAlignBlock objects to distinguish separate blocks. Define a zmenu for the Region and individual Blocks for GenomicAlignBlock objects (not ConstrainedElements). Group together elements from low coverage species. Added cigar string to enable the display of cigar glyphs.
Bio/EnsEMBL/GlyphSet/_alignment_pairwise.pm => Added full target_species alignment parameters to align variable
EnsEMBL/Web/Component.pm => Split check_for_align_errors into 2 methods: check_for_align_in_database and check_for_missing_species.
EnsEMBL/Web/Component/Compara_Alignments.pm => Parse the align parameter to extract the target species and target slice. Group the alignments according to group_id and dbID. Draw a table to select overlapping alignments.
EnsEMBL/Web/ZMenu/MultipleAlignment.pm => Added full target_species alignment parameters to align variable. Added This region and This block entries to the zmenu
EnsEMBL/Web/ZMenu/PairwiseAlignment.pm => Added full target_species alignment parameters to align variable
Use external link for private data instead of internal 'properties' link
75 changes for GeneTrees and start of changes for Family
Improvements to stats tables - readthrough counts with glossary mouseover
Tweak to accept 'Chr' as well as 'chr' in chromosome names
Remove no longer unused Family/Proteins/'from the tree
Tidying up of Gene/Family/Proteins? and Multi/Family/Details?
Removed deprecated calls
New images for variation view (provided by Denise)