lib/igc: Parse HFDTE line from IGC files
model/igcfile: Save HFDTE header as date_utc
model/igcfile: Added NOT NULL flag to date_utc column

/flights/igc_headers should be called before applying this patch to fill
the empty date_utc column
lib/analysis: Extracted from_seconds_of_day() function
igcfile: Added timestamps and locations columns
lib/sql: Added extract_array_item() function
lib: Added rasteralchemy library

This library adds basic support for the PostGIS 2 raster type and the
related GiST-based index
model: Added elevations table

Data can be added to the table through the built-in raster2pgsql script
flights: Show elevation in barogram and fix data table