Admin view for software indicator

Closes #293

Changes:

• Data model: dimensions, attributes and levels now identified by ID, per-year dimensions (and therefore indirectly per-year attributes and levels)
• Database views: new views attributes_with_dimensions, levels_with_attributes_and_dimensions and software_evaluations
• Database functions: new aggregate weighted_avg to calculated weighted average (discarding null values), new function update_software_indicator_attributes to set attribute weights, weighted average of attribute scores in calculation of dimension scores
• Tests: basic tests for database calculations in 998-test-software-indicator.sql
• Admin page: non-integer minimum required dimension scores (editable in table and radar plot), basic edit form for attribute weights, dropdown to select year
• Software evaluation page: dropdown to select year
• API: new parameter evaluation_year to specify year
• useSoftwareIndicator hook: mapping to old data structures (identification by name) to keep component code intact (for now!)