Write import logs to file instead of database.

[Ed McDonagh]

Refs #21 where currently the verbose output logs are being stored in the database. Create a file instead and write to that, and offer it for download.

[Ed McDonagh]

Now creates a log file and writes to it instead of the database. Need to add code to allow download of log and to delete it along with the uploaded file. Refs #100.

→ <<cset 6fe76a57a1a6>>

[Ed McDonagh]

Logfile field now contains filename and path from MEDIA_ROOT. Reuses existing download function in place for exports. Fixes #100.

→ <<cset ffa3872ca6ed>>

[Ed McDonagh]

Removed the log field from the database. Refs #100.

→ <<cset 567604d71132>>

[Ed McDonagh]

Merge of issue ref #100 moving the patient size import logs from the database to text files.

→ <<cset 5f3815152e9e>>