save_filecontent revised

Fixed:
* Rare but potential db file damage when tmp file cannot be put out.
* Now shows updated message.
* Now deletes db and text file if valid lines in the file became zero
and inform such result.
Merge pull request #24 from Tatsuya-Nonogaki/master

save_filecontent revised
show and save_filecontent revised

Fixed:
* There had been no way to newly create source list file.
* Now save_filecontent has nearly the same procedures as my previous
save_listcontent patch.
Merge pull request #25 from Tatsuya-Nonogaki/master

show and save_filecontent revised
Merge remote-tracking branch 'origin/master' into filter-integra