Don't check for number of returned rows.

Fixes #61.
Fixes #68.
See #69.
DB: Use COUNT(*) instead of numRows()

ownCloud's internal ```numRows()``` function is not ideal and will most
likely be deprecated in the future. Use the database internal COUNT(*)
function instead.
Merge branch 'master' into v1.3
Harmonize size calculation with Firefox browser

Use base 1024 for k, M, G,... instead of base 1000 (SI units). This
results in harmonized size display with the Firefox browser.

The relevant functions in Firefox are:
* [gSyncQuota.loadData()](http://hg.mozilla.org/mozilla-central/file/9e03cd21db08/browser/base/content/sync/quota.js#l27)
* [DownloadUtils.convertByteUnits()](http://hg.mozilla.org/mozilla-central/file/9e03cd21db08/toolkit/mozapps/downloads/DownloadUtils.jsm#l452)

Fixes #58.
Merge branch 'harmonize_quota_usage_size' into v1.3