Commit 2021-10-05 10:10 da4d5501

chore(measure_theory/*): better names and notations, add easy lemmas (#9554)

• Localize notation for absolutely continuous in the measure_theory namespace, and add separate notations for the case of measures and of vector measures.
• Standardize some names, using measure instead of meas.
• Add two lemmas on measures with density.