size info handling

[kosarko]

We more or less allow the size info to be a free text. What we had (now manually curated) was a mix of different number formats - including decimals with dot or comma as a separator, various multipliers (M,m, k, K...), space or comma as a thousand separator.

We should implement some or all of the following:

• [x] regex or some other check of the entered values (#987 )
• [ ] curation task that would help find those with bad format
• [ ] nicer formating in the item view, e.g. 120000000 -> 120M or 120 000 000
• [ ] if the field is to be used for searching or faceting we need a common format (and maybe have it as an int field in solr)