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
Merge pull request #15 from muffato/feature/compara_species_sets

Compara species sets
Merge pull request #9 from muffato/feature/taxon_name

Bugfix: taxon names in the gene-tree displays
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
Merge pull request #23 from ens-lgil/master

Replace the url action 'Summary' by 'Explore' for Variation and Structur...
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
Merge branch 'master' of https://github.com/Ensembl/ensembl-webcode
75 changes for GeneTrees and start of changes for Family
Merge pull request #22 from muffato/feature/compara_wga_stats

Feature/compara wga stats
Merge pull request #25 from kathryn-beal/master

Master