feat(notes): Add simple measure documentation

From documents in DB, requires more attention and revision.

03-documentation/measures.md

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+# Measures
+
+TODO:: separation of shares, inequality indices and ratios
+
+**absolute** shows magnitude of difference between subgroups of pop -> focus on absolute welfare
+
+**relative** shows proportional difference between subgroups of pop -> focus on welfare in relation to others
+
+## Common ones
+
+### Vertical
+
+Gini coeff, Theil, entropy measure, atkinson indexes
+
+### Horizontal
+
+mean differences between groups; ratios between better off/worse off
+
+GGini; GTheil; GCOV
+
+
+## All indicators
+### Absolute
+
+* quantiles (division by 5) / deciles (division by 10) / centiles (division by 100)
+
+* Absolute Gini index 
+    * ?
+
+* Standard deviation 
+    * deviations from norm in *absolute* terms
+
+### Relative
+
+
+* ratios of quantiles to each other (division of various quantiles)
+
+* Gini coefficient:
+    * based Lorenz curve - population percentage versus accumulated fractions of wealth
+    * is area between lorenz curve and perfect equality
+    * needs: individual/household income/wealth; pop size
+
+* Theil index:
+    * how much income distribution (person x receives y from total income) is away from perfect uniform distribution
+    * log -based
+    * can be disaggregated into subgroups
+    * Theil L > weighting factors are population groups; Theil T > weighting factors are fraction of appropriated income
+
+* Atkinson measures:
+    * measures cumulative deviation of each income in relation to average income value in distribution
+
+* Palma ratio:
+    * dividing share of income/wealth held by top 10% by bottom 40%, thus high = bad
+
+* s80s20, s40s20 ratios:
+    * ?
+
+* Concentration index:
+    * divide whole pop by 100 to find percentiles
+    * then you know how many ppl are in each group and add their total income
+
+* Foster-Greer-Thorbecke-class distribution (@Sotomayor2021)
+
+## Horizontal
+
+