[Tracker] Use gettext plural forms

[Luca Ferretti <elle uca libero it>]

I'm updating Italian translation, I found those:

#: ../src/tracker-utils/tracker-files.c:141
#: ../src/tracker-utils/tracker-files.c:199
#: ../src/tracker-utils/tracker-meta-folder.c:268
#: ../src/tracker-utils/tracker-query.c:254
#: ../src/tracker-utils/tracker-search.c:221
#: ../src/tracker-utils/tracker-search.c:260
#: ../src/tracker-utils/tracker-tag.c:382
#: ../src/tracker-utils/tracker-unique.c:231
#, fuzzy, c-format
msgid "Result: %d"

#: ../src/tracker-utils/tracker-files.c:142
#: ../src/tracker-utils/tracker-files.c:200
#: ../src/tracker-utils/tracker-meta-folder.c:269
#: ../src/tracker-utils/tracker-query.c:255
#: ../src/tracker-utils/tracker-search.c:222
#: ../src/tracker-utils/tracker-search.c:261
#: ../src/tracker-utils/tracker-tag.c:383
#: ../src/tracker-utils/tracker-unique.c:232
#, fuzzy, c-format
msgid "Results: %d"

-------
#: ../src/tracker-utils/tracker-info.c:202
msgid "Unable to retrieve data for %d uris"

#: ../src/tracker-utils/tracker-info.c:211
msgid "No metadata available for all %d uris"

Isn't better use gettext plural forms?

Note, maybe there are other occurrences where plural form could be
good, check PO/POT files