Allow for custom attributes and read type description of fastq

[cgirardot]

Implements #86

Allows to add "schema_attribute[tag]" (e.g. sample_attribute[treatment]) in the input schema tables (tsv only) where the schema ('sample', 'run', 'experiment', 'study') e.g. a new sample_attribute[treatment] column in the ena_sample.tsv. These extra headers are injected in the XML generation stream, and injected in the generated XML as a ATTRIBUTE sequence (templates where modified accordingly). For samples, only the default ERC000011 was modified to support these additional attributes. Unit is not yet supported.

Additionally, support for read_type and read_label (as new headers in the ena_run.tsv) is added to the run XML for files of type fastq to support single cell situations where more than 2 fastq files are available (ENA then requires to have read_type described). Multiple values can be passed using CSV format eg paired,cell_barcode

Limitations: read_label is not fully supported as it would require to support SpotDescriptorType in the run XML but it is unclear how this information could be passed. Basic support for SPOT_DECODE_SPEC with a READ_SPEC using BASE_COORD (see SRA.common.xsd) could be provided with:

• headers like READ_SPEC 1...READ_SPEC n where the header number is the READ_SPEC's READ_INDEX
• value would be formatted like READ_LABEL:READ_CLASS:READ_TYPE:BASE_COORD:SPOT_LENGTH. For example: UMI1:Application Read:Other:1:8.