report: add abstract

doc/report/abstract.tex

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+Organizational data extracted from mathematical libraries has the
+potential to be usable in the design of a universal search engine for
+mathematical knowledge. However, it is not enough to only extract this
+data into a unified format, it is also necessary to make this data
+easily available. The project \emph{ulo-storage} which this report
+documents had the aim of doing just that. Collect various pieces of
+exported data sets into a centralized and efficient store, make that
+storage engine available as a publicly available endpoint and then
+evaluate different ways of querying that store.