NgIf syntax has been extended to support else clause to display template
when the condition is false. In addition the condition value can now
be stored in local variable, for later reuse. This is especially useful
when used with the `async` pipe.
Example:
```
<div *ngIf="userObservable | async; else loading; let user">
Hello {{user.last}}, {{user.first}}!
</div>
<template #loading>Waiting...</template>
```
closes#13061closes#13297
When compiling libraries, this feature extracts the minimal information
from the directives/pipes/modules of the library into `.ngsummary.json` files,
so that applications that use this library only need to be recompiled
if one of the summary files change, but not on every change
of the libraries (e.g. one of the templates).
Only works if individual codegen for libraries is enabled,
see the `generateCodeForLibraries: false` option.
Closes#12787
Removes `CompileIdentifierMetadata.name` / `.moduleUrl`,
as well as `CompileTypeMetadata.name / moduleUrl` and
`CompileFactoryMetadata.name / moduleUrl`.
Tobias Bosch
Chuck Jazdzewski
Victor Berchet
Misko Hevery
Victor Savkin
vsavkin