refactor(library/hott): remove unnecessary generalizations
fix(shell/CMakeLists.txt): merge into a single lean.js file
feat(frontends/lean): reserve notation, closes #95
refactor(library): use 'reserve' notation in the standard library
feat(frontends/lean): allow 'reserve' inside namespaces
feat(frontends/lean): validate infixl/infixr/postfix/prefix declarations against reserved notations
refactor(library/hott/path): use HoTT book notation for path concatenation and inverse
feat(frontends/lean): do not allow user to define notation using tokens `!` and `@`, closes #248
fix(kernel/converter): remove buggy eta-reduction and rely only on eta-expansion

The bug is exposed by new unit test
fix(shell/lean.cpp): use temp ios
checkpoint